The objectives of the program are to define the ways by which red cells can readjust their volume by alterations in the fluxes and concentrations of Na ion, K ion, and Ca2 ion ions. Furosemide, ouabain and chlorpromazine affect fluxes of these cations and the influence of these agents on volume regulation will be investigated. Volume regulation in abnormal red cells in hereditary stomatocytosis, hereditary spherocytosis, sickle cell anemia and thalassemia will be characterized. Bibliographic references: J.S. Wiley, C. Hsieh, C.C. Shaller and R.W. Colman. Thrombin induces release of K ion from lysosomes of human platelets. Fed. Proc. 34:222, (1975); J.S. Wiley and R.A. Cooper. Effect of membrane cholesterol on the cotransport system for Na ion plus K ion in the human erythrocyte. Fed. Proc. 34:237, (1975).